剑指offer33 把数组排成最小的数

class Solution {
public:
    string PrintMinNumber(vector<int> numbers) {
        vector<string> str;
        for(int i = 0;i < numbers.size();i++){
            char ch[999];
            sprintf(ch,"%d",numbers[i]);
            str.push_back(ch);
        }
        sort(str.begin(),str.end(),cmp);
        string s;
        for(int i = 0;i < str.size();i++)
            s += str[i];
        return s;
    }
    static bool cmp(string a,string b){
        return a+b < b+a;
    }
};

char tmp = numbers[i] + ‘0‘;
str.push_back(tmp);

string tmp = numbers[i] + ‘0‘;
str.push_back(tmp);

string tmp = to_string(numbers[i]);
str.push_back(tmp);